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1.
Anton Lamboj Oliver Lucanus Patrick Osei Darko J. Pablo Arroyo-Mora Margaret Kalacska 《Biotropica》2020,52(5):896-912
Remote sensing has become an integral and invaluable tool to inform biodiversity conservation and monitoring of habitat degradation and restoration over time. Despite the disproportionately high levels of biodiversity loss in freshwater ecosystems worldwide, ichthyofauna are commonly overlooked in favor of other keystone species. Freshwater fish, as indicators of overall aquatic ecosystem health, can also be indicators of larger scale problems within an ecosystem. As a case study with multi-temporal, multi-resolution satellite imagery, we examined deforestation and forest fragmentation around the Atewa Forest Reserve, Ghana. Within small creeks, Limbochromis robertsi, a unique freshwater cichlid with an extremely limited distribution range, can be found. Historically, the land cover in the area has undergone substantial deforestation for agriculture and artisanal small-scale mining. In the 1389-km2 study area, we found deforestation accelerated along with increased forest fragmentation in the 2014–2017 period (167.4 km2 of deforestation) with the majority of the forest loss along the river and creek banks due to small-scale mining operations and increased agriculture. Field visits indicated a decrease in the total L. robertsi population by approximately 90% from the early 1990s to 2018. Its distribution has been reduced to higher elevations by anthropogenic habitat barriers at low elevations and the presence of predatory species. Loss of riparian forest through land use and cover change to mining and agriculture contributes to the habitat degradation for this endemic species. Fine spatial- and temporal-scale studies are required to assess habitat characteristics are not captured by global- or continental-scale datasets. 相似文献
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Jessica L. Forrest Eric W. Sanderson Robert Wallace Teddy Marcelo Siles Lazzo Luis Humberto Gómez Cerveró Peter Coppolillo 《Biotropica》2008,40(3):285-294
This study examines how human land uses and biophysical factors serve as predictors of land cover change in and around Madidi National Park in Bolivia. The Greater Madidi Landscape ranges over an elevational gradient from < 200 m in the Amazon basin to 6000 m in the high Andes, contains more than ten major ecosystem types, and several protected areas and sustainable use zones. In this study, Landsat Thematic Mapper satellite images collected over the study area at the beginning of the 1990s and then the 2000s were classified according to broad land cover types. Below elevations of 3000 m, the landscape experienced equal rates of deforestation and secondary forest increases of approximately 0.63 percent annually, resulting in no significant net change. Below elevations of 1000 m, however, we found an annual net loss in forest cover of 0.11 percent. Across the landscape, land cover change was most likely to occur near areas previously deforested, near roads and population centers, and at low elevations. We found net deforestation rates to be inversely related to strength of natural resource protection laws in protected areas and other jurisdictions. Results suggest little net change for the landscape as a whole, but that local scale changes may be significant, particularly near roads. Management policies favorable for biodiversity conservation in this landscape should limit the building of new roads and immigration to biologically sensitive areas and continue to support protected areas, which are achieving a positive result for forest conservation. 相似文献
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David S. Wilkie 《Human ecology: an interdisciplinary journal》1994,22(3):379-403
The rate of rain forest clearing throughout central Africa is of national and international interest because it affects both the region's contribution to global warming and impacts the sustainable productive capacity of its natural resource base. The size and inaccessibility of much of central Africa makes remote sensing imagery the most suitable data source for regional land cover mapping and land transformation monitoring. Present image availability is poor. Most regional studies have had to rely on coarse resolution AVHRR 1 km data that fails to detect the small-scale agricultural clearings that are the primary cause of land cover change throughout the region. This study demonstrates that higher spatial resolution Landsat MSS imagery, which comprises the most available, geographically comprehensive and longest time series dataset, is too coarse to map land cover in low population density areas typical of most of central Africa. Furthermore, this study cautions that the use of high resolution imagery without detailed collateral field data on population density and land use practices while generating superficially plausible results, will most probably produce highly inaccurate estimates of land cover and land transformation. Policies for future regional remote sensing surveys of central Africa should focus on acquisition of higher spatial, spectral, and radiometric resolution imagery and must be accompanied by detailed, systematic field data collection. 相似文献
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Lyndon Estes Peng Chen Stephanie Debats Tom Evans Stefanus Ferreira Tobias Kuemmerle Gabrielle Ragazzo Justin Sheffield Adam Wolf Eric Wood Kelly Caylor 《Global Change Biology》2018,24(1):322-337
Land cover maps increasingly underlie research into socioeconomic and environmental patterns and processes, including global change. It is known that map errors impact our understanding of these phenomena, but quantifying these impacts is difficult because many areas lack adequate reference data. We used a highly accurate, high‐resolution map of South African cropland to assess (1) the magnitude of error in several current generation land cover maps, and (2) how these errors propagate in downstream studies. We first quantified pixel‐wise errors in the cropland classes of four widely used land cover maps at resolutions ranging from 1 to 100 km, and then calculated errors in several representative “downstream” (map‐based) analyses, including assessments of vegetative carbon stocks, evapotranspiration, crop production, and household food security. We also evaluated maps’ spatial accuracy based on how precisely they could be used to locate specific landscape features. We found that cropland maps can have substantial biases and poor accuracy at all resolutions (e.g., at 1 km resolution, up to ～45% underestimates of cropland (bias) and nearly 50% mean absolute error (MAE, describing accuracy); at 100 km, up to 15% underestimates and nearly 20% MAE). National‐scale maps derived from higher‐resolution imagery were most accurate, followed by multi‐map fusion products. Constraining mapped values to match survey statistics may be effective at minimizing bias (provided the statistics are accurate). Errors in downstream analyses could be substantially amplified or muted, depending on the values ascribed to cropland‐adjacent covers (e.g., with forest as adjacent cover, carbon map error was 200%–500% greater than in input cropland maps, but ～40% less for sparse cover types). The average locational error was 6 km (600%). These findings provide deeper insight into the causes and potential consequences of land cover map error, and suggest several recommendations for land cover map users. 相似文献
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基于TM的渤海海岸带1988～2000年生态环境变化 总被引：2，自引：0，他引：2
海岸带作为海陆之间的过渡地带,是全球生态环境最为复杂和特殊之处。研究海岸带土地利用变化对于了解该区域生态环境演变具有重要意义。利用1988和2000年的Landsat-TM数据,在GIS技术支持下,通过一系列空间分析,得到渤海海岸带土地利用/土地覆盖变化,结合社会经济统计资料分析该区域生态环境的动态变化情况及其驱动因素。结果表明,1988~2000年,由于渤海海岸带社会经济的快速发展,海岸带土地利用格局发生了巨大的变化。耕地大面积减少,城乡工矿用地、养殖池塘、盐田急剧扩张;林地、湿地等具有重要生态价值的土地类型面积显著下降。表明强烈的人类活动已经使自然生态系统受到破坏,渤海海岸带生态环境质量总体上呈现下降趋势。 相似文献
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《Ecohydrology》2018,11(4)
Grasslands have been modified and replaced worldwide and have affected water regulation ecosystem services. In order to support public policies attending to the consequences of different grassland modifications and replacements, general patterns and models about their consequences on water regulation are needed. We quantitatively meta‐analysed the results of 110 site‐specific studies analysing infiltration (83) and evapotranspiration (28) responses to grasslands alterations by grazing, crops, and afforestation and how these responses vary with environmental factors. In grasslands, soil water infiltration is significantly reduced by grazing and cropping on average by 51% and 57%, respectively. Water infiltration is increased by 65% in response to afforestation. The reduction of infiltration with grazing decreases with soil sand content and increases with the mean annual precipitation (PPT) and the ratio PPT/mean annual potential evapotranspiration. The replacement of grasslands by forests increases evapotranspiration by 30%, and the variation of this response was linearly related to PPT and the PPT/mean annual potential evapotranspiration ratio. There was a negative trend in evapotranspiration responses although not significant, when grasslands were replaced by crops or modified by grazing. Our meta‐analysis was able to reveal average patterns and the influence of local climate and soil properties on eco‐hydrological responses to grasslands modifications and replacements, which have not been previously described. These results may support general predictive models on the influence of land use changes and ecosystem services provision. Significant gaps were found in the number of studies, especially of evapotranspiration, precluding the achievement of a general conclusion regarding evapotranspiration and infiltration responses. 相似文献
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The carbon budget of the tropics has been perturbed as a result of human influences. Here, we attempt to construct a ‘bottom‐up’ analysis of the biological components of the budget as they are affected by human activities. There are major uncertainties in the extent and carbon content of different vegetation types, the rates of land‐use change and forest degradation, but recent developments in satellite remote sensing have gone far towards reducing these uncertainties. Stocks of carbon as biomass in tropical forests and woodlands add up to 271 ± 16 Pg with an even greater quantity of carbon as soil organic matter. Carbon loss from deforestation, degradation, harvesting and peat fires is estimated as 2.01 ± 1.1 Pg annum?1; while carbon gain from forest and woodland growth is 1.85 ± 0.09 Pg annum?1. We conclude that tropical lands are on average a small carbon source to the atmosphere, a result that is consistent with the ‘top‐down’ result from measurements in the atmosphere. If they were to be conserved, they would be a substantial carbon sink. Release of carbon as carbon dioxide from fossil fuel burning in the tropics is 0.74 Pg annum?1 or 0.57 MgC person?1 annum?1, much lower than the corresponding figures from developed regions of the world. 相似文献
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福建省长汀县曾是我国南方红壤地区水土流失最严重的县份之一,经过20多年的艰辛努力,长汀已成为中国水土流失治理的典范.采用遥感技术和景观格局分析技术,基于1988、1998、2004、2009和2011年的遥感影像,对长汀县水土流失最为严重的河田盆地区进行土地利用动态变化检测与景观格局变化分析.结果表明,研究区在这23a间的土地利用发生了很大变化,其中最主要的特征就是以针叶林为主的林地面积的快速增长和地表裸土面积的大幅下降.景观分析表明,水土流失治理新增的小块林地正逐渐形成连片分布,而裸土面积在大幅减少的同时,其斑块也趋于破碎.总的看来,这23a间的水土流失治理已使得研究区的生态明显趋于好转. 相似文献
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Multiple Methods in the Study of Driving Forces of Land Use and Land Cover Change: A Case Study of SE Kajiado District,Kenya 总被引：1，自引：0，他引：1
David J. Campbell David P. Lusch Thomas A. Smucker Edna E. Wangui 《Human ecology: an interdisciplinary journal》2005,33(6):763-794
This landscape-scale study combines analysis of multitemporal satellite imagery spanning 30 years and information from field
studies extending over 25 years to assess the extent and causes of land use and land cover change in the Loitokitok area,
southeast Kajiado District, Kenya. Rain fed and irrigated agriculture, livestock herding, and wildlife and tourism have all
experienced rapid change in their structure, extent, and interactions over the past 30 years in response to a variety of economic,
cultural, political, institutional, and demographic processes. Land use patterns and processes are explored through a complementary
application of interpretation of satellite imagery and case study analysis that explicitly addresses the local–national spatial
scale over a time frame appropriate to the identification of fundamental causal processes. The results illustrate that this
combination provides an effective basis for describing and explaining patterns of land use and land cover change and their
root causes. 相似文献
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STOÉCIO M. F. MAIA STEPHEN M. OGLE CARLOS E. P. CERRI CARLOS C. CERRI 《Global Change Biology》2010,16(10):2775-2788
The southwestern portion of the Brazilian Amazon arguably represents the largest agricultural frontier in the world, and within this region the states of Rondônia and Mato Grosso have about 24% and 32% of their respective areas under agricultural management, which is almost half of the total area deforested in the Brazilian Amazon biome. Consequently, it is assumed that deforestation in this region has caused substantial loss of soil organic carbon (SOC). In this study, the changes in SOC stocks due to the land use change and management in the southwestern Amazon were estimated for two time periods from 1970–1985 and 1985–2002. An uncertainty analysis was also conducted using a Monte Carlo approach. The results showed that mineral soils converted to agricultural management lost a total of 5.37 and 3.74 Tg C yr?1 between 1970–1985 and 1985–2002, respectively, along the Brazilian Agricultural Frontier in the states of Mato Grosso and Rondônia. Uncertainties in these estimates were ±37.3% and ±38.6% during the first and second time periods, respectively. The largest sources of uncertainty were associated with reference carbon (C) stocks, expert knowledge surveys about grassland condition, and the management factors for nominal and degraded grasslands. These results showed that land use change and management created a net loss of C from soils, however, the change in SOC stocks decreased substantially from the first to the second time period due to the increase in land under no‐tillage. 相似文献
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Reducing emissions from deforestation and forest degradation (REDD+) requires developing countries to quantify greenhouse gas emissions and removals from forests in a manner that is robust, transparent, and as accurate as possible. Although shifting cultivation is a dominant practice in several developing countries, there is still very limited information available on how to monitor this land‐use practice for REDD+ as little is known about the areas of shifting cultivation or the net carbon balance. In this study, we propose and test a methodology to monitor the effect of the shifting cultivation on above‐ground carbon stocks. We combine multiyear remote sensing information, taken from a 12‐year period, with an in‐depth community forest carbon stock inventory in Palo Seco Forest Reserve, western Panama. Using remote sensing, we were able to separate four forest classes expressing different forest‐use intensity and time‐since‐intervention, which demonstrate expected trends in above‐ground carbon stocks. The addition of different interventions observed over time is shown to be a good predictor, with remote sensing variables explaining 64.2% of the variation in forest carbon stocks in cultivated landscapes. Multitemporal and multispectral medium‐resolution satellite imagery is shown to be adequate for tracking land‐use dynamics of the agriculture‐fallow cycle. The results also indicate that, over time, shifting cultivation has a transitory effect on forest carbon stocks in the study area. This is due to the rapid recovery of forest carbon stocks, which results in limited net emissions. Finally, community participation yielded important additional benefits to measuring carbon stocks, including transparency and the valorization of local knowledge for biodiversity monitoring. Our study provides important inputs regarding shifting cultivation, which should be taken into consideration when national forest monitoring systems are created, given the context of REDD+ safeguards. 相似文献
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Matthias Baumann Ignacio Gasparri María Piquer‐Rodríguez Gregorio Gavier Pizarro Patrick Griffiths Patrick Hostert Tobias Kuemmerle 《Global Change Biology》2017,23(5):1902-1916
Carbon emissions from land‐use changes in tropical dry forest systems are poorly understood, although they are likely globally significant. The South American Chaco has recently emerged as a hot spot of agricultural expansion and intensification, as cattle ranching and soybean cultivation expand into forests, and as soybean cultivation replaces grazing lands. Still, our knowledge of the rates and spatial patterns of these land‐use changes and how they affected carbon emissions remains partial. We used the Landsat satellite image archive to reconstruct land‐use change over the past 30 years and applied a carbon bookkeeping model to quantify how these changes affected carbon budgets. Between 1985 and 2013, more than 142 000 km2 of the Chaco's forests, equaling 20% of all forest, was replaced by croplands (38.9%) or grazing lands (61.1%). Of those grazing lands that existed in 1985, about 40% were subsequently converted to cropland. These land‐use changes resulted in substantial carbon emissions, totaling 824 Tg C between 1985 and 2013, and 46.2 Tg C for 2013 alone. The majority of these emissions came from forest‐to‐grazing‐land conversions (68%), but post‐deforestation land‐use change triggered an additional 52.6 Tg C. Although tropical dry forests are less carbon‐dense than moist tropical forests, carbon emissions from land‐use change in the Chaco were similar in magnitude to those from other major tropical deforestation frontiers. Our study thus highlights the urgent need for an improved monitoring of the often overlooked tropical dry forests and savannas, and more broadly speaking the value of the Landsat image archive for quantifying carbon fluxes from land change. 相似文献
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《Ecohydrology》2018,11(4)
Fire may alter land cover throughout the landscape and affect run‐off responses to rainfall events in a burnt watershed. Therefore, the challenge is to understand the interactions between forest composition and fire patterns in a karstic, Mediterranean watershed that affects the run‐off regime. The aim of this research is to improve the understanding of the interactive effects of wildfire and land‐cover change on the rainfall–run‐off relationship in a first‐order watershed. To achieve this goal, satellite imagery, official spatial data, and hydrological modelling were used to study forest composition in relation to extreme fire and to simulate run‐off response for 2 rainfall events. The results show that an extreme wildfire had a greater impact on planted forest, composed mostly of pines, than on native species. Additionally, it was found that the land‐cover alternation due to fire affected the run‐off regime and contributed to an increase in maximum discharge and run‐off volume for the 2 rainfall events by ~39–47%. During the regeneration period, the run‐off response for the 2 rainfall events decreased by ~7.7–9%. Wildfires may impact the run‐off response more profoundly as the plantation of pine trees increases. A greater increase in run‐off response may endanger infrastructure in terms of flooding and affect the population well‐being. Watershed management in areas where afforestation is considered should focus on planting native species that are less flammable rather than introducing combustible pines, thus reducing the hydrologic impacts of land‐cover alteration due to wildfire, especially when climate warms and wildfires become more frequent and intense. 相似文献
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全球土地计划第二次开放科学大会于2014年3月19日至21日在德国柏林举行,来自世界50个国家的650位学者参加了大会,大会主题为\"土地变化:全球挑战与地方现实\"。大会分四大主题进行,设103个分会场,以口头报告、快速演讲、展板等形式展开。有关\"土地变化再思考\"这一主题的探讨,主要围绕土地变化监测、土地变化数据集、土地变化模型构建、遥感技术的应用四方面展开,强调土地变化研究中新技术、新方法的使用,展示了不同国家在土地变化研究中的最新研究方法与研究成果,提出未来土地变化研究面临的机遇和挑战。大会对我国土地变化研究的启示主要有以下几方面:(1)引入多类型数据源监测我国土地利用变化,以适应不同尺度、不同类型、不同目标的土地变化研究;(2)加强国内土地变化数据集的建设,避免数据优劣共存、系统性差、类型不全面等问题;(3)加强土地变化模型构建,改进数据输入、加强模型验证、提高模型预测精度;(4)加强卫星遥感技术的应用,使不同空间尺度、不同时间尺度遥感数据和地方数据相结合,加强数据分析与处理能力。 相似文献
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The amount of carbon released to the atmosphere as a result of deforestation is determined, in part, by the amount of carbon held in the biomass of the forests converted to other uses. Uncertainty in forest biomass is responsible for much of the uncertainty in current estimates of the flux of carbon from land‐use change. In the present contribution several estimates of forest biomass are compared for the Brazilian Amazon, based on spatial interpolations of direct measurements, relationships to climatic variables, and remote sensing data. Three questions were posed: First, do the methods yield similar estimates? Second, do they yield similar spatial patterns of distribution of biomass? And, third, what factors need most attention if we are to predict more accurately the distribution of forest biomass over large areas? The answer to the first two questions is that estimates of biomass for Brazil's Amazonian forests (including dead and belowground biomass) vary by more than a factor of two, from a low of 39 PgC to a high of 93 PgC. Furthermore, the estimates disagree as to the regions of high and low biomass. The lack of agreement among estimates confirms the need for reliable determination of aboveground biomass over large areas. Potential methods include direct measurement of biomass through forest inventories with improved allometric regression equations, dynamic modelling of forest recovery following observed stand‐replacing disturbances, and estimation of aboveground biomass from airborne or satellite‐based instruments sensitive to the vertical structure plant canopies. 相似文献